Definition 4.2 (query space)  [1]}.
Let \(Q\)  be a function that maps every set \(S\subseteq P\)  to a corresponding set \(Q(S)\) , such that \(Q(T)\subseteq Q(S)\)  for every \(T\subseteq S\) .
Let \(f:P\times Q(P)\rightarrow \mathbb {R}\)  be a cost function.
The tuple \((P,w,Q,f)\)  is called a query space.
